Contractable ram mandrels



July 5, 1960 G. H. DALRYMPLE 2,943,729

CONTRACTABLE RAM MANDRBLS Filed May 18, 1956 I N V EN TOR. GEORGE H 041.EVMPL E BY W W z W United States Patent CONTRACTABLE RAM MANDRELS GeorgeH. Dalrymple, Seatfle, Wash, assignor to Boeing Airplane Company,Seattle, Wash., a corporation of Delaware Filed May 18, 1956, Ser. No.585,778

6 Claims. (Cl. 205-7) This invention pertains to a mandrel which iscontractable from a normal size for insertion in a tube to support itwhile being pushed through a constricting die.

Standard tube making machines frequently do not form tubes; to closetolerances. For certain applications, however, it is important that thedimensions of tube diameter and particularly external tube diameter bequite exact, such for example as when such tubes are to be bent inbending machines of some types. Otherwise it is found that the portionof a tube at the inner side of a bend, particularly if of small radius,will be creased or corrugated, which is undesirable. It has thereforebeen the practice to constrict oversize tubes by a sizing operationwhere exact dimensions are required. The sizing is accomplished byforcing the tube through a constricting die of proper size. In suchoperations it has been customary' to clamp the tube end in some fashion,which would prevent the clamped end of the tube from passing through theconstricting die. It was therefore necessary to cut off and discard thegripped end of the tube.

The principal object of the present invention is to provide a mandrelwhich will engage a tube end both to support hand to push the tubethrough a constricting die which will enable the entire tube to bepushed through the die, so as to eliminate the necessity of cutting offa piece of the tube end, which both wastes tubing and requires an extraoperation following the sizing operation.

More specifically it is an object to provide a resiliently contractablemandrel which can be fitted into an end of a .tube to be constricted,and which will abut the tube end so as to push it through theconstricting die, but which is small enough so that the mandrelsupported portion of the tube can be moved through the die, and whichwill contract during such movement so as to enable the mandrel supportedportion of the tube to be constricted.

A further object is to provide such a contractable mandrel which is ofsimple construction and economical to manufacture.

Another object is to provide such a mandrel which can be insertedreadily into a tube prior to constriction of the tube, which willsupport the tube adequately for pushing it through a constricting die,and which can be removed easily from the constricted tube following thesizing operation.

These objects can be accomplished by a mandrel incorporating a segmentedhead, the segments of which are received respectively between the finsof a resilient spider, deformable to enable the segments to contractcollectively. The cluster of segments is integrated by encircling bands,and the segments have bosses cooperating to abut a tube end' forexerting on it thrust in a direction lengthwise of the tube.

Figure 1 is a top perspective view of tube constricting apparatusutilizing" a contractable ram mandrel, parts of such apparatus beingbroken away.

. Figure 2 is a transverse sectional view through the mandrel, taken online 22 of Figure 3, and Figure 3 is a side elevation view of themandrel with the segmented head being shown in section along line 3-3 ofFigure 2.

The sizing apparatus comprises a bed 1 on one end of which is mountedthe constricting die 2. This die may be shifted along ways 3 to anappropriate location, depending upon the length of the tube T to besized, and secured in the proper adjusted position by a latch 4engageable with an appropriate cleat 5. At the other end of the-bed 1 afluid pressure cylinder 6 is mounted, in which is received a piston forthe purpose of reciprocating the piston rod 7 of the ram.

The tube T is pushed through the constricting die 2 by the mandrel Mshown generally in Figure l and in detail inFigures 2. and 3. Thismandrel is engaged with the tube and is supported and reciprocated by aconnecting bar 8 extending between the mandrel and a reciprocablecarriage 9. This carriage supports one end of the connecting bar 8 andis connected to the end of connecting rod 7 to transmit reciprocatorymotion to the connecting bar. The carriage is guided for movement on thetracks 10. For the purposes of the present invention it is assumed thatthe constricting die, the ram, the connecting bar and the carriagedescribed above are all conventional. This invention is directed to theparticular type of tube supporting anddriving mandrel M.

The mandrel includes a shank 11 having a hollow end which can receive acomplemental end of a connecting bar 8' and be connected to it by abayonet joint incorporating the angle slots 12 capable of receiving pinsprojecting radially from the end of connecting bar 8. The mandrel shankmay be. secured to the connecting bar against relative rotation by a setscrew 13.

. The important structure of the mandrel is carried by the shank ll andincludes a contractable mandrel head H in'sertable within the end of thetube T upon contraction. This head preferably is of segmented typeincorporating a plurality of hard and preferably metal segments 14arranged in a cluster and resiliently mounted. As shown best in FigureZ,each of the segments is of arcuate shape, but is of considerable'radialextent. Such segments are intergrated by one or more encircling bands,two 0-- rings 15 of elastomer material being shown as confining the.segments. Such rings are spaced axially of the segments, and the outersides of the segments are grooved to receive such rings.

The segments14 are clustered about a rod tip 16 pro-- The jectingaxially from the shank 11 of the mandrel. segments are mounted forresilient radial movement relative to the rod tip by interposing betweensuch tip and the segments a spider of elastomer material including anannular hub 17 closely embracing the rod tip 16 and havingcircumferentially spaced radial fins 1'8 projecting radially About theroot of the rod tip 16 is a backingflange 19 against which the ends ofthe segments 14 abut. This-- flange is integral with the shank 11 sothat prmsure exerted by the pistonlwithincylinder 6 and transmittedthrough the connecting bar 8 to the mandrel may in turn be transmittedby the flange 19 directly to the segments 14.

Patented July 5, 1960:

The elastomer material of which the Such segments maytransmit thisthrust force to the tube by bosses 20, projecting outward from the outersides of the mandrel head segments adjacent to the flange 19, which canabut the tube end. The segments are retained on the rod tip by provisionof an annular rib 21 adjacent to the flange 19 portions of which rib arereceived in notches or grooves 22 formed in the inner sides of thesegments 14.

Prior to insertion of the segmented mandrel head H into a tube end, theresilient'spider 17, 18 will be substantially relaxed, so as toh'oldthesegments-14 in-the r outermost positions. These'gments are retainedin their clusteredrelationship against axial movementbyi nterengagementof the rib'21 and grooves 22 and are-confined against radially outwardmovement by the-bands 15. If radially inward. pressureis exertedcollectively on thesegments, boththe hub- 17 and, because-of theoutwardly flared cross-sectionof thesegments, the fins 18 of theresilient spiderwill'be deformed. By the resultingradially inwardmovementtbf the segments- 14 the fins 18 will becontractedcircumferentially and distended radially. The hub 17, on the contrarywil-l be contracted radially and will-seek to expand circumferentially.In order to facilitate such deformation of'the spider the inner sides ofthe' segments 14- are relieved, such as-by being providedwith chamfers23, as shown in Figure 2. Because the elements ofthe spider are notappreciably compressible, although they are readily deformable, it willbe evidentthat as a practical matter the radially inward movement of thesegments 14 will be limited to quite asmallrange. When in relaxedcondition, therefore, the segmented mandrel head shouldhave an externaldiameter only slightly larger than the internal diameter of the tube Tto besized.

To facilitate insertion of the segmented mandrel head H into the end ofa tube itis preferred that the radially inward constricting force forcontracting the mandrel head be effected by the act of inserting suchhead into the tube end. To produce such a radiallyinward force the endsof the segments 14 remote from the'flange 19 are chamfered at 2.4 so asto provide a cooperatively tapered end on the mandrel head. As such headis forced axially against the end of the tube, therefore, the tube endwill effect a wedging action on the chamferedends of the segments anddraw them radially inward against the resilient resistance of thedeformable spider 17, 18. Continued application of axial force-willcause the segments to slide the tapered entering end of the mandrelfully into the tube and inserting movement of the'm-andrel head willcontinue until the bosses 20 are brought into abutment with the tube endWall.

It is preferred that the flange 19'be smaller than the largest portionof the segmented mandrel head H when in its condition of greatestcontraction. Alsotheprojection of the bosses 20 beyond the adjacentportionsof the outer surfaces of the segments: should be less than thethickness of the thinnest tube T in which the mandrel is to be engaged.With a mandrel having'suchproportions the entire mandrel as well as-theentire tube T can be pushed through a sizing die 2, while the mandrel iscontracted and confined within the tube end. When the tube has thus beenmoved completely throughthe die, it can be withdrawn from the mandreland can be used in its entirety.

When the tube has been withdrawn from the contractable mandrel head H,itwvill be evident that the resilience of spider 17, 18 will immediatelyexpand the mandrelhead again until the stress in the spider is virtuallycompletely relieved, but the bands will retain the segments in theirclustered relationship. Inithis relaxed condition shown in Figure 3 thegreatest diameter of the mandrel head should not exceed the outer:diameter of the tube T, and consequently should not exceed appreciably,if at all, the opening through the .die 2. Ifin such relaxedconditionthe mandrel headis smaller than the die opening, the head can bewithdrawn through the die Without change of shape and without thenecessity of removing the mandrel from the connecting bar 8. If the endsof the segments 14 adjacent to flange 19 are chamfered as at 25 inFigure 3, the mandrel may be withdrawn through the opening of die 2anyway, because engagement of the mandrel segment chamfers 25 with thedie would simply contract the mandrel head sufliciently so that it couldbe withdrawn through the die opening.

I claim as my invention:

1. A mandrel comprising a shank, a spider of resiliently deformableelastomer material supported by said shank and including acentralrportionvand fins integral with and radiating from said centralportion, and a segmented head includinga plurality ofsegmentsreceivedrespectively between. the fins of said spider and yieldingly movabletoward the central portion of said spider against the resistance of saidcentral portion and fins of said spider deformed thereby. v

2. The mandrel'defined' in claim 1, in-which the segments have relievedinner sides facilitating deformation of the central portion of thespider upon movement of the segments toward the central portion of thespider.

3. A mandrel comprising a shank and an endcarried by said shank,-including a rod tip, a backing flange at the root ofsaid tip; a spiderof resiliently deformable elastomer material including a hubportion'mounted-on said tipand radial fins-integral withandradiating-from said hulb portion, a segmented head includingapluralityof arcuate segments received respectively between the fins of saidspider and yieldingly movable toward said hub portion against theresistance of said hub portion and fins of said spider deformedthereby,and means retaining each such segment in a position engageable with theface of said backing flange adjacent to said rod tip.

4. A mandrel comprising a'shank and an end carried by said shank;includinga rod tip, a backing flangeat the root of saidtip, an annularrib adjacent to the root of said tip, a spider of resiliently deformableelastomer .material including a hub portion mounted on said'tipengageablewith the face of-said backing flange adjacent tosaid rodtip.

5. A mandrel comprising a plurality of segments arranged in an annularcluster and-having' circumferentially adjacent sides ofcircumferentially adjacent segments spaced apart circumferentiallyand-the inner surfaces of opposite segments spaced apart, resilientlycontractable means disposed radially inwardly of said segments, engagedby innersurface portions thereof and yieldable inward to enable conjointcontracting movement of saidsegments When-inwardpressure' is exerted ontheir outer sides, and resilient means received betweencircumferentiaily adjacent portions of circumferentially adjacentsegments and contractable circumferentially by inward movement of saidsegments.-

6. A mandrel comprising a plurality of separate, outwardly flared, rigidsegments arranged an-annular cluster to be bisected respectively byradii of the annulus in which they are arranged andhaving'circumferentially adjacent sides of circumferentially adjacentsegments spaced apart circumferentially and the innersurfaces ofopposite segments spaced apart, and means resiliently contractable froman unstressed condition, received inthe spaces between suchcircumferentially adjacent sides of the circumferentiallyv adjacentsegments, engaged with such segmentsides and contractable.circumferentially under .Stress by wedging pressure of said segmentsthereagainst by inward movement of said segments when inward pressure isexerted on their outer sides.

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